You have the 3¢ Lincoln from the years 1923-30. It is a common stamp and is worth no more than a couple of dollars whether used or unused. Taking the easily identifiable varities first;

The stamp has the letters Kans. on it

The value of this stamp (#661) can be found by clicking here.

The stamp has the letters Nebr. on it

The value of this stamp (#672) can be found by clicking here.

The stamp has no perforations on top AND bottom

The value of this stamp (#600) can be found by clicking here.

The stamp has perforations on three or more sides
and you count ten perforations along the bottom

The value of this stamp (#584) can be found by clicking here.

The stamp has perforations on three or more sides
and you count eleven perforations along the bottom

To determine the difference in the perforations between #555 and #635 you will need a copy of the very common 1932 3¢ Washington (#720). A picture of which is shown below. Follow the instructions below

The value of #555 can be found by clicking here.
The value of #635 can be found by clicking here.